Database

# # |\\ There are many kinds of Database management systems. like: MySQL, MongoDB, Oracle .....

# hence, we'll learn SQL (Structured Querry Language)

# in SQL we use table to store data in a organized way

# Columns are Vertically and Rows are Horizontally

# |||||||||| Selecting Column ||||||


# to select all of the Column in SQL we have to type " Select * from (table name)"
# hence, we can select a specific Column by defining its name like " Select Name from (table name)"
# and we can also see or select multiple Columns at a time, like " Select Email, Password, Friends from Users"


# ||||||||||| Selecting Row ||||||||||||



# to select one specific Row we can use the 'Where' clause like " Select * from Users (table name) Where id = 2"
# notice that here, 'Where' works almost like Python 'if' condition, we can give any conditon after 'Where' in SQL
# to get all users that have more than 100 friends. You can write the query like below..


# " Select * from Users Where friends < 100 "

# and we can use multiple conditions after the 'Where' clause, using 'or' 'and' like>..

# " Select * from Users Where id > 3 and friends < 100" # " Select * from Users Where id > 3 or friends > 100"


# |||||||||||||| SQL Functions ||||||||||

# if we want to get the sum of every row, that means we want to add the values of every friends column's numbers
# " SELECT SUM(Friends) From Users "

# some SQL functions including SUM: # 1. AVG() # 2. COUNT() # 3. FIRST() # 4. LAST() # 5. MAX() # 6. MIN() # 7. SUM()

# HERE, COUNT() is special if we pass any column name , it will return the Rows number of the selected Columns :D